New methods for producing nylon 6,6 fibers with enhanced mechanical properties.

摘要

Aliphatic polyamides are very important thermoplastic polymers. They exhibit good mechanical properties and therefore these polymers are suitable in many industrial applications. To improve mechanical properties of these polymers, many of efforts focusing on orientation and crystallinity have been made. These two important parameters can be improved by increasing draw ratios. However, it is difficult to overcome traditional low draw ratios for polyamides due to strong hydrogen bonding between amide linkages in the polymer chains. Many approaches have been attempted to suppress hydrogen bonding in polyamides. Plasticizers such as ammonia, iodine, salts and several spinning methods such as dry spinning, wet spinning, gel spinning, and dry-jet wet spinning have been investigated. More specialized methods for obtaining high modulus aliphatic polyamides such as vibrational zone drawing/annealing, as well as laser heating zone drawing/annealing, are also discussed. A new technique that involves the dry-jet wet spinning and drawing of GaCl3/nylon 66 complex has been developed. This new method allows traditional low draw ratios for nylon 66 to be increased by disrupting the interchain hydrogen bonded network. Fibers with a very high modulus and strength were obtained when high molecular weight nylon 66 was used. Solid state polymerization (SSP) of nylon 66 is reported to obtain high molecular weight nylon 66. It was found that the polymerization temperature is the most the most important factor that controls the final molecular weight of the polymer. The kinetics of SSP are also investigated by using various experimental conditions. Low (30,000 g/mole) and high molecular weight (170,000 g/mole) nylon 66 were used to prepare, nano-scale non-wovens by using an electrospinning technique. The experiments showed that a mixed solvent consisting of formic acid and chloroform is a good medium for electrospinning nylon 66. Fiber diameter increased and fiber diameter distribution was broader with increasing polymer concentration for both low and high molecular weight nylon 66. Initial moduli of electrospun webs improved for high molecular weight nylon 66 particularly when a low polymer concentration of 3% was used. This study demonstrated that the use of high MW nylon 66 is a simple approach for improving the mechanical properties of electrospun filaments.